I wonder if you could throw a small microcontroller at the bottom of a canal, powered by water passing through a fan, to hide it. And why you would want to do that.

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lexicality 4 hours ago | parent | next [-]

canals have negligible water flow (except during disasters!) so I don't think that'd work very well. They also get dredged occasionally so there's a decent chance anything you leave down there won't last more than a couple of years

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DonHopkins an hour ago | parent | next [-]

> They also get dredged occasionally

And it's fascinating to watch!

https://www.youtube.com/watch?v=aGFC6MF5-_k

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fragmede 4 hours ago | parent | prev [-]

They do have tides though, so make it a big fan that points up.

	▲	wbl 22 minutes ago \| parent [-]
		Depends on the canal. The UK narrow boat network has locked everywhere so minimal current in most sections similarly the Netherlands. In fact most canals. But then you have something like Suez which is just open to the ocean.

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ErroneousBosh 6 hours ago | parent | prev [-]

Water quality monitoring. Communicate back to the surface with ultrasonic pulses.

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arnsholt 4 hours ago | parent [-]

And in case people think ultrasonic signaling isn’t a real thing, it very much is. In the oil and gas industry, it’s how measurements taken while drilling a hole are sent back to the surface through the drilling mud.

	▲	doodlebugging 2 hours ago \| parent [-]
		Downhole tools used in MWD/LWD do not use ultrasonic frequencies. Drilling is a very noisy environment. The first tool that I used employed a downhole pulser with a surface transducer and operated at about 0.5-1 Hz. That's not ultrasonic. It was a pretty low frequency signal. Data transmission rates limit the volume of information that can be transmitted from the downhole tool to the surface where they are decoded. Your tool has to set up a pressure wave in the mud column that is detectable miles away from the tool while the well is being drilled. This is a good recent paper authored by an experienced drilling engineer about MWD/LWD drilling history and pulser designs and data rates that can be expected. https://www.aade.org/application/files/1917/4604/2319/AADE-2...